Humidifier with a water tub within a pressurized chamber

ABSTRACT

A tub is configured to contain a supply of water and is configured to be inserted into a chamber of a humidifier. The tub includes a tub base configured to contain the supply of water. The tub also includes a tub lid and a flow plate provided between the tub base and the tub lid. The flow plate includes a water level indicator configured to indicate a level of the supply of water in the tub base. In addition, the water level indicator includes a generally rectangular portion and a generally triangular portion.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/194,634, filed Jun. 28, 2016, now pending, which is a continuation ofU.S. application Ser. No. 14/157,639, filed Jan. 17, 2014, now U.S. Pat.No. 9,402,970, which is a continuation of U.S. application Ser. No.12/737,926, filed Mar. 1, 2011, now U.S. Pat. No. 8,631,789, which isthe U.S. National Phase of International Application No.PCT/AU2009/001232 filed on Sep. 17, 2009 and which claims priority toU.S. Applications 61/097,765, filed Sep. 17, 2008 and 61/226,134, filedJul. 16, 2009, the entire contents of each being incorporated herein byreference.

The entire contents of U.S. application Ser. No. 12/397,850, filed Mar.4, 2009, are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to systems and method to control thehumidity of breathable gases used in all forms of respiratory apparatusventilation systems including invasive and non-invasive ventilation,Continuous Positive Airway Pressure (CPAP), Bi-Level therapy andtreatment for sleep disordered breathing (SDB) conditions such asObstructive Sleep Apnea (OSA), and for various other respiratorydisorders and diseases.

BACKGROUND OF THE INVENTION

Respiratory apparatuses commonly have the ability to alter the humidityof the breathable gas in order to reduce drying of the patient's airwayand consequent patient discomfort and associated complications. The useof a humidifier placed between the flow generator and the patient maskproduces humidified gas that minimizes drying of the nasal mucosa andincreases patient airway comfort. In addition in cooler climates, warmair applied generally to the face area in and about the mask is morecomfortable than cold air.

Many humidifier types are available, although the most convenient formis one that is either integrated with or configured to be coupled to therelevant respiratory apparatus. While passive humidifiers can providesome relief, generally a heated humidifier is required to providesufficient humidity and temperature to the air so that the patient willbe comfortable. Humidifiers typically comprise a water tub having acapacity of several hundred milliliters, a heating element for heatingthe water in the tub, a control to enable the level of humidification tobe varied, a gas inlet to receive gas from the flow generator, and a gasoutlet adapted to be connected to a patient conduit that delivers thehumidified gas to the patient's mask.

Typically, the heating element is incorporated in a heater plate whichsits under, and is in thermal contact with, the water tub.

SUMMARY OF THE INVENTION

One aspect of the invention is a respiratory apparatus that comprises ahumidifier for humidifying a flow of breathable gas to be delivered to apatient in which a tub of the humidifier is insulated to reduce thetemperature of the water and the power consumed by the apparatus.

Another aspect of the invention is a humidifier for a respiratoryapparatus that includes a chamber that is pressurizable to reduce thepressure on joints of the humidifier tub to reduce leaks.

A further aspect of the invention is a humidifier for a respiratoryapparatus that includes a chamber that is pressurizable to reducetolerances for insertion of a tub with respect to seals on an inlet andan outlet tube of the humidifier chamber.

A still further aspect of the invention is a humidifier for arespiratory apparatus that directs air over the surface of a supply ofwater contained in a tub to humidify a flow of breathable gas regardlessof the water level.

Another aspect of the invention is a humidifier for a respiratoryapparatus that includes seals that are not under the supply of water,thus reducing a risk of leakage.

A still further aspect of the invention is a humidifier for arespiratory apparatus that prevents water from spilling back into a flowgenerator, or blower, that generates a flow of breathable gas.

Yet another aspect of the invention is a humidifier for a respiratoryapparatus that includes a tub that is disposable.

Another aspect of the invention is a humidifier for a respiratoryapparatus that includes a tub that is cleanable and/or reusable.

Still another aspect of the invention is a humidifier for a respiratoryapparatus that includes a tub that comprises a water level indicator,for example a water level indicator that indicates a maximum fill level.Yet another aspect of the invention relates to a water level indicatorthat may be removable from the tub. A still further aspect of theinvention relates to a water level indicator in a tub that may be viewedthrough a window of the humidifier. An even further aspect of theinvention relates to a water level indicator that appears to changecolor as the water level changes, for example appears to be a darkercolor or mixture of colors.

Another aspect of the invention is a humidifier for a respiratoryapparatus that is connectable to a heated or non-heated tube fordelivery of the humidified flow to a patient.

A further aspect of the invention relates to a tub that is removablefrom the humidifier and is configured to prevent any water flowing outof the tub from flowing back into the flow generator.

According to a sample embodiment, a humidifier for humidifying a flow ofbreathable gas to be delivered to a patient comprises a chamberconfigured to receive the flow of breathable gas; a tub configured tocontain a supply of water, the tub being configured to be inserted intothe chamber; a lid provided on the chamber and being movable between anopen position and a closed position; and a seal provided on the lid, theseal being configured to seal the chamber such that the flow ofbreathable gas pressurizes the chamber.

According to yet another sample embodiment, a tub for insertion into ahumidifier chamber comprises a tub base configured to contain a supplyof water; a tub lid; a flow plate; and a seal connected to the flowplate, wherein the flow plate is positioned between the tub base and thetub lid via the engagement of the seal with side wall edges of the tubbase and side wall edges of the tub lid.

According to a further sample embodiment, a respiratory apparatus forproviding a humidified flow of breathable gas to a patient comprises aflow generator to generate a flow of breathable gas and a humidifierand/or a tub as described above.

According to another sample embodiment, a humidifier for humidifying aflow of breathable gas to be delivered to a patient comprises a chamberconfigured to receive the flow of breathable gas; a tub configured tocontain a supply of water, the tub being configured to be inserted intothe chamber; and a lid provided on the chamber and being movable betweenan open position and a closed position. The tub comprises a tub baseconfigured to contain a supply of water; a tub lid; and a flow plateprovided between the tub base and the tub lid, wherein the flow platecomprises a water level indicator configured to indicate a level of thesupply of water in the tub base.

According to a still further sample embodiment, a tub is configured tocontain a supply of water and to be inserted into a chamber of ahumidifier. The tub comprises a tub base configured to contain a supplyof water; a tub lid; and a flow plate provided between the tub base andthe tub lid, wherein the flow plate comprises a water level indicatorconfigured to indicate a level of the supply of water in the tub base.The water level indicator comprises a generally rectangular portion anda generally triangular portion. The generally triangular portioncomprises an angled wall that extends at least partially below the flowplate and the angled wall comprises a drain hole and indicia.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described with reference to theaccompanying drawings, in which:

FIG. 1 schematically depicts of a respiratory apparatus including a flowgenerator and humidifier according to a sample embodiment of theinvention;

FIG. 2 schematically depicts the humidifier of FIG. 1 with the lid inthe closed position;

FIG. 3 schematically depicts the humidifier of FIG. 1 with the lid inthe open position;

FIG. 4 schematically depicts a partial exploded assembly view of thehumidifier of FIG. 1;

FIG. 5 schematically depicts a cradle of the humidifier of FIG. 4;

FIG. 6 schematically depicts a lid closure member of the humidifier;

FIG. 7 schematically depicts an electrical connector and tube connectorof the humidifier of FIG. 1;

FIG. 8 schematically depicts the cradle and humidifier bottom of thehumidifier of FIG. 1;

FIG. 9 schematically depicts the humidifier cradle and the humidifierbottom of FIG. 8 in an assembled configuration;

FIG. 10 schematically depicts an inner plate of the humidifier of FIG.1;

FIG. 11 schematically depicts a latch plate of the humidifier of FIG. 1;

FIG. 12 schematically depicts the humidifier of FIG. 1 including anoutlet tube;

FIG. 13 schematically depicts a sealing ring for the humidifier outlettube of FIG. 12;

FIG. 14 schematically depicts the outlet tube of the humidifier of FIG.12;

FIG. 15 schematically depicts the humidifier of FIG. 1 including theinner plate, the outlet tube, and the tube connector;

FIG. 16 schematically depicts the lid and the seal of the humidifier ofFIG. 1;

FIG. 17 schematically depicts the seal of FIG. 16;

FIG. 18 schematically depicts a side view cross section of thehumidifier of FIG. 1;

FIG. 19 schematically depicts a water tub including a tub base and aflow plate of the humidifier of FIG. 1;

FIG. 20 schematically depicts a bottom perspective view of the flowplate of FIG. 19;

FIG. 21 schematically depicts an exploded assembly of a tub, includingthe tub base and flow plate of FIG. 19, according to one sampleembodiment;

FIG. 22 schematically depicts the assembled tub of FIG. 21;

FIG. 23 schematically depicts a cross section of the tub of FIG. 22;

FIG. 24 schematically depicts a section view of the tub of FIG. 22;

FIG. 25 schematically depicts a seal between the flow plate and the tubbase of the tub of FIG. 21;

FIG. 26 schematically depicts a tub according to another sampleembodiment;

FIG. 27 schematically depicts an exploded assembly view of the tub ofFIG. 26;

FIG. 28 schematically depicts a plan view of the tub of FIGS. 26 and 27;

FIG. 29 schematically depicts a cross section along line 29-29;

FIG. 30 schematically depicts a cross section along line 30-30;

FIG. 31 schematically depicts a bottom perspective of the flow plate andthe tub lid in an assembled condition;

FIG. 32 schematically depicts a cross section of the flow plate and thetub lid of FIG. 31;

FIG. 33 schematically depicts a detailed view of the connection of theflow plate to the tub lid;

FIG. 34 schematically depicts a cross section of the tub in theassembled condition, including the tub base;

FIG. 35 schematically depicts a connection of the tub base, the flowplate, and the tub lid;

FIG. 36 schematically depicts a perspective of the tub in the assembledcondition;

FIG. 37 schematically depicts a top perspective of the flow plate;

FIG. 38 schematically depicts a bottom perspective of the flow plate;

FIG. 39 schematically depicts a plan view of the flow plate;

FIG. 40 schematically depicts a cross section along line 40-40;

FIG. 41 schematically depicts a bottom view of the flow plate;

FIG. 42 schematically depicts an assembly of the flow plate and seal;

FIG. 43 schematically depicts a plan view of the flow plate;

FIG. 44 schematically depicts a cross section along line 44-44;

FIG. 45 schematically depicts a bottom view of the flow plate;

FIG. 46 schematically depicts the maximum water level indicator of theflow plate;

FIG. 47 schematically depicts a cross section of the maximum water levelindicator on the flow plate;

FIG. 48 schematically depicts a detailed view of a wedge of the bridgeof the flow plate;

FIG. 49 schematically depicts a detailed view of the maximum water levelindicator;

FIG. 50 schematically depicts a perspective view of a tub according toanother sample embodiment;

FIG. 51 schematically depicts another perspective view of the tub ofFIG. 50;

FIG. 52 schematically depicts a top view of the tub of FIG. 50;

FIG. 53 schematically depicts an exploded assembly of the tub of FIG.50;

FIG. 54 schematically depicts an exploded assembly of the tub of FIG. 50from another perspective;

FIGS. 55a and 55b schematically depict cross sections of the tub of FIG.50;

FIG. 56 schematically depicts a perspective view of a flow plate of thetub of FIG. 50;

FIG. 57 schematically depicts another perspective view of the flow plateof FIG. 56;

FIG. 58 schematically depicts a top view of the flow plate of FIGS. 56and 57;

FIG. 59 schematically depicts a bottom view of the flow plate of FIGS.56-58;

FIGS. 60a-60c schematically depict a water level indicator usable withthe flow plate of FIGS. 56-59;

FIG. 61 schematically depicts a perspective view of the flow plate andwater level indicator of FIGS. 56-60 c with the tub lid of the tub ofFIGS. 50-55;

FIG. 62 schematically depicts another perspective view of the flowplate, water level indicator and tub lid of FIG. 61;

FIG. 63 schematically depicts an exploded assembly of a tub, includingthe tub base and flow plate of FIG. 19, according to another sampleembodiment;

FIG. 64 schematically depicts the assembled tub of FIG. 63;

FIG. 65 schematically depicts a cross section of the tub of FIG. 64;

FIG. 66 schematically depicts a section view of the tub of FIG. 64;

FIG. 67 schematically depicts a seal between the flow plate and the tubbase of the tub of FIG. 63;

FIG. 68 schematically depicts an exploded assembly of a tub according toanother sample embodiment;

FIGS. 69 schematically depicts an exploded assembly of the tub of FIG.68 from another perspective;

FIG. 70 schematically depicts a perspective view of the tub of FIGS. 68and 69;

FIG. 71 schematically depicts another perspective view of the tub ofFIGS. 68 and 69;

FIG. 72 schematically depicts a section of the tub of FIGS. 68-71;

FIG. 73 schematically depicts a heated air delivery hose, tube, orconduit, including a cuff having a humidifier connector;

FIGS. 74 and 75 schematically depict the air delivery hose, tube, orconduit of FIG. 73 including a cuff to connect the hose, tube, orconduit to a patient interface, such as a mask; and

FIG. 76 schematically depicts a cross section of the hose, tube, orconduit and cuff of the FIGS. 56 and 57.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

Respiratory Apparatus

Referring to FIG. 1, a respiratory apparatus 10 comprises a flowgenerator, or blower, 12 and a humidifier 14. The humidifier 14comprises a humidifier chamber 16 and a lid 18 which is pivotablebetween an open and a closed position. A water chamber, or tub, 20 isprovided in the humidifier chamber 16 and is covered by the lid 18 whenthe lid 18 is in the closed position. A seal 19 is provided to the lid18, as shown in more detail in FIG. 15. The lid 18 includes a window 30to allow visual inspection of the contents of the humidifier tub 20. Theseal 19 includes an aperture 31 that corresponds to the position of thewindow 30 of the lid 18.

The tub 20 comprises a tub lid 86 that is configured to direct a flow ofbreathable gas generated by the flow generator 12 along a channel 90 andthrough an outlet 92 of the channel 90 into the tub 20, as described inmore detail below. The tub 20 includes an outlet 88 for the humidifiedflow of breathable gas to a tube configured to deliver the humidifiedflow to a patient interface, e.g. a mask.

Humidifier

As shown in FIG. 2, the humidifier 14 is connectable to the flowgenerator 12 by connectors, or latches, 24. The latches 24 may be, forexample, spring biased latches that engage corresponding recesses (notshown) in the flow generator 12. An electrical connector 26 is providedto electrically connect the flow generator 12 to the humidifier 14.Electrical power may be provided from the flow generator 12 to thehumidifier 14, although it should be appreciated that the humidifier maybe provided with its own power source. Control signals may also beprovided from the flow generator 12 to the humidifier 14 through theelectrical connector 26.

It should be appreciated that the humidifier 14 may include its owncontrol system, for example, a microprocessor provided on a printedcircuit board (PCB). The PCB may be located in the wall of thehumidifier chamber 16 and may include a light, e.g. an LED, toilluminate the contents of the tub 20 to permit visual inspection of thewater level. Referring to FIG. 4, an aperture 35 may be provided in thewall of the humidifier chamber 16 to allow the light on the PCB toilluminate the humidifier chamber 16. The aperture 35 is covered with acover 37 to prevent access to the PCB and the light (e.g. LED) from thehumidifier chamber 16. The cover 37 may be transparent or colored toprovide a colored light, such as a green light to appear within thehumidifier chamber 16. The light is provided to shine into thehumidifier chamber 16 to allow the water level in the water tub 20 to beseen. Alternatively, multiple lights may be located on the PCB toprovide different indications regarding the heating of the humidifier,for example an amber light may be provided to indicate that thehumidifier is heating up to a required temperature and a blue light maybe provided to identify when the humidifier is at the requiredtemperature.

The humidifier 14 comprises the humidifier chamber 16 and the lid 18which is pivotally connected to the humidifier chamber 16. As shown inFIGS. 3 and 4, the lid 18 comprises a hinge portion 17 that is hinged tohinge portions 47 provided on the humidifier chamber 16. Referring toFIG. 3, a humidifier bottom 54 is provided to the humidifier chamber 16,as shown in more detail in FIG. 8. An opening member 28 is provided forreleasing the lid 18 to allow the lid to be pivoted to the open positionas described in more detail below.

Referring again to FIGS. 3 and 4, the lid 18 comprises catches 15 thatare configured to be engaged by the latches 44 to maintain the lid inthe closed position. The seal 19 also comprises wedge-shaped protrusions13 that are configured to engage the water tub 20, for example the tublid 86, when the lid 18 is in the closed position to push the tub 20 ina direction (e.g. laterally) toward an outlet 34 of the humidifierchamber 16 to assist in forming a seal between the water tub outlet 88and the humidifier chamber outlet 34. A domed portion 11 is alsoprovided on the seal 19 to push the water tub 20 against a heating plate36 when the lid 18 is in the closed position. A circular seal section,or sealing ring, 21 is also provided to the seal 19 to seal, when thelid 18 is in the closed position, a tub emptying aperture 89 provided inthe tub lid 86.

Referring again to FIGS. 2 and 4, the humidifier chamber 16 alsoincludes an air inlet 22 configured to receive the flow of breathablegas generated by the flow generator 12 when the humidifier 14 isconnected to the flow generator 12 by the latches 24. The inlet 22directs the flow into the channel 90 (see FIGS. 1, 3 and 21-24) in thetub lid 86 of the water tub 20. The flow is directed by the channel 90to the outlet 92 into the water tub 20.

As shown in FIGS. 4 and 5, the humidifier chamber 16 comprises ahumidifier cradle 32 that includes the air inlet 22. The humidifiercradle 32 also includes the humidifier chamber outlet 34 to allow thehumidified flow to be delivered to a delivery hose, tube, or conduitthat is configured to be connected to the humidifier to deliver thehumidified flow to a patient. The outlet 34 is provided in a back sideof the humidifier cradle 32. It should be appreciated that the outlet 34may be provided on a side of the humidifier cradle 32. Such amodification would also entail modifying the water tub 20 to align theoutlet 88 of the tub 20 with the outlet 34 of the humidifier cradle 32.

Referring to FIG. 4, the heating plate 36 is provided to heat the watersupply contained in the humidifier chamber 16. A cradle bottom 40 isprovided beneath the heating plate 36 and an insulation layer 38 isprovided between the heating plate 36 and the cradle bottom 40. Theheating plate 36 may be formed, for example, of a nickel chrome alloy oranodized aluminum that allows the heating plate 36 to be formed thinnerthan currently available heating plates and with a larger surface area.The heating plate 36 may also include a thermistor that is controlled bya control circuit, for example, provided on the PCB.

Referring to FIGS. 4-6, the humidifier cradle 32 supports a lid closuremember 42 that is movable between an open position and a closedposition. The lid opening member 28 is provided at an end of the lidclosure member 42 as shown in FIG. 6. The lid closure member 42comprises latches 44 that are configured to engage catches 15 of the lid18 and retain the lid 18 in the closed position. The lid closure member42 comprises a rod, or post, 48 that supports a spring 46 that biasesthe lid closure member 42 into the closed position. To open the lid 18,the opening member 28 is pushed by the user against the bias of thespring 46, to the right in FIG. 5, to move the latches 44, and the lidclosure member 42, to the open position. When the user releases the lidopening member 28, the bias of the spring 46 returns the lid closuremember 42 and the latches 44 to the closed position.

The lid closure member 42 is supported by a front retaining wall 33 ofthe cradle 32. The lid closure member 42 includes tabs 45 that engageslots 41 formed in the front retaining wall 33. The front retaining wall33 also comprises slots 39 through which the latches 44 protrude. Theslots 39, 41 accommodate sliding movement of the lid closure member 42and the latches 44 and the tabs 45, respectively, engaged with the slots39, 41.

As shown in FIG. 7, the electrical connector 26 is connected to aplurality of wires 52, for example, three wires, that are connected to atube connector 50 that is shown in FIG. 15 and described in more detailhereinafter. The tube connector 50 comprises a plurality of contacts 78that correspond in number to a number of wires 52 and are each connectedto a respective wire. Although three wires 52 and three contacts 78 areshown in the drawings, it should be appreciated that a different numberof wires and contacts may be provided, for example, two wires and twocontacts. The tube connector 50 allows for the connection of a heatedtube, for example, such as disclosed in U.S. patent application Ser. No.11/936,822, filed Nov. 8, 2007, the entire contents of which areincorporated herein by reference.

As shown in FIGS. 8 and 9, the humidifier cradle 32 is supported by achamber bottom 54 of the humidifier chamber 16. The chamber bottom 54comprises a pair of latches 56 that are configured to engagecorresponding catches (not shown) on the back of the humidifier cradle32 to secure the humidifier cradle 32 to the chamber bottom 54. Thechamber bottom 54 also includes a bottom opening 58 through which thebottom of the humidifier cradle 32 extends. The chamber bottom 54 isconfigured to cover the wires 52 and the lid closure member 42 whenconnected to the cradle 32, as shown in FIG. 8.

Referring to FIGS. 9-11, an inner plate 60 may be secured to thehumidifier cradle 32 over the latches 24 and the electrical connection26. As shown in FIG. 10 the inner plate 60 includes a plurality ofapertures 62 that are configured to allow the latches 24 to extendtherethrough and an aperture 64 configured to allow the electricalconnector 26 to extend therethrough. The inner plate 60 also comprises apair of apertures 66 that are configured to receive fasteners, forexample, threaded fasteners 80 (FIG. 15), to secure the inner plate 60to the humidifier cradle 32. A boss 68 may also be provided on the innerplate 60 to receive a fastener, for example, a threaded fastener 80 forsecuring the inner plate 60 to the humidifier cradle 32. The inner plate60 provides spillback protection to prevent water spilling back from thehumidifier 14 to the flow generator 12.

As shown in FIG. 11, the latches 24 are provided on a latch plate 23that is provided between the humidifier cradle 32 and the inner plate60. An end of the latch plate 23 is secured to a plate 25 that is alsoprovided between the humidifier cradle 32 and the inner plate 60. Theplate 25 comprises posts 29 that support springs 27 that are configuredto bias the latch plate 23 so that the latches 24 extend through theapertures 62 of the inner plate 60 in the positions shown in FIG. 9.When the humidifier 14 is connected to the flow generator 12 the latches24 engage catches (not shown) provided on the flow generator 12 and thelatches 24, and subsequently the latch plate 23, are pushed against thebias of the springs 27 (to the right in FIG. 9). Once the latches 24fully engage the catches, the springs 27 bias the latch plate 23 and thecatches 24 back to their starting position shown in FIG. 9 with thelatches 24 engaged with the catches of the flow generator 12. When thehumidifier 14 is connected to the flow generator 12, the electricalconnector 26 connects with a corresponding electrical connector (notshown) in the flow generator 12 to permit the flow generator 12 toprovide power and/or control signals to the humidifier 14. As shown inthe figures, the electrical connector 26 may comprise a terminal, orterminals, although it should be appreciated that the electricalconnector 26 may comprise a contact, or contacts, that are received interminals in the flow generator 12.

Referring to FIGS. 12-14, the humidifier cradle 32 may comprise anoutlet tube 70 provided through the outlet 34. As shown in FIG. 14, theoutlet tube 70 may comprise a flange 72 that is configured to engage theback wall 55 of the humidifier cradle 32 and a groove 74 that isconfigured to receive a sealing ring 76 shown in FIG. 13. The outlettube 70 may be removed to allow replacement of all wet area parts of thehumidifier, for example, the tub 20 and the outlet tube 70. The outlettube 70 may also be made out of a material that can be sterilized. Itshould be appreciated that the outlet tube 70 may also be disposable.

Referring to FIGS. 15 and 16, in the closed position the lid 18 providedwith the seal 19 allows the humidifier chamber 16 to be sealed andbecome pressurized by the flow generator 12 when the flow generatorgenerates a flow of air through the inlet 22 of the humidifier 14.Pressurizing the humidifier chamber 16 reduces the pressure on thejoints on the tub 20 to reduce leaks. Pressurizing the humidifierchamber 16 also reduces tolerances for insertion of the tub 20 withrespect to seals on the inlet 22 and the outlet tube 70 of thehumidifier chamber 16. The humidifier chamber 16 also insulates the tub20 to provide enhanced thermal properties and reduce power consumption.Insulating the tub 20 also reduces heat loss to the surroundings. Thehumidity output of the humidifier is determined directly from the watertemperature. As the heat loss from the tub to the surroundings isreduced due to insulating the tub, less power is needed to reach thewater temperature corresponding to a desired humidity output. Inaddition, incoming air is preheated as it passes the outside walls ofthe tub, before it enters the tub, which also reduces the power requiredto reach the water temperature corresponding to the desired humidityoutput.

As also shown in FIG. 15, the inner plate 60 is secured to thehumidifier cradle 32 by the threaded fasteners 80, although it should beappreciated that other fastening members or methods may be used tosecure the inner plate 60 to the humidifier cradle 32. It should beappreciated that other latching structures and systems may be used toreleasably secure the lid. For example, push to close and button to openoperation systems may be used. Other examples include, but are notlimited to, a rod latching system, a rotating latch or a hooking latch.

The outlet tube 70 and the tube connector 50 provide the ability toconnect both a standard tube and a heated tube. As shown in FIG. 15, thetube connector 50 and the contacts 78 are provided separately from theoutlet tube 70. A heated tube having corresponding electricalconnections, e.g. terminals, may be provided in a rotational snap fitwith the tube connection 50. This type of connection provides ease ofconnection and reduces the tolerance stack of the respiratory apparatus10. A heated tube 134 suitable for connection to and use with thehumidifier 14 is described in more detail with reference to FIG. 31. Asshown in FIG. 15, a cover 132 may be connected to the back wall of thehumidifier to cover the tube connector 50, and the contacts 78, when anon-heated tube is connected to the outlet tube 70. The cover 132 may beformed of a pliable rubber or other suitable flexible material.Alternatively the cover 132 may be a separate component not attached tothe humidifier that may be inserted over the connector 50.

Referring to FIGS. 17 and 18, the seal 19 comprises a groove 51configured to receive a corresponding edge, or rim, 57 of the lid 18 toconnect the seal 19 to the lid 18. The wedge-shaped protrusions 13 (seealso FIG. 3) are configured to engage the tub lid 86 when the lid 18 isin the closed position to bias the water tub 20 toward the back wall ofthe humidifier chamber 16 so that the outlet 88 is in sealing engagementwith the outlet tube 70. The seal 19 also comprises a sealing rim 49that extends around the perimeter of the seal 19 and is configured toseal the perimeter of the lid 18 when the lid is in the closed position.An inner sealing rim 53 is provided around the aperture 31 of the seal19 to seal around the window 30 of the lid 18.

Humidifier Tub-Disposable-First Embodiment

Referring to FIGS. 19 and 20, the water tub 20 comprises a tub base 82and a flow plate 84. The flow plate 84 comprises a dividing plate 96that comprises an inlet 98 that is configured to receive the flow ofbreathable gas directed by the channel 90 of the tub lid 86. The outlet92 of the channel 90 is configured to direct the flow into the inlet 98of the dividing plate 96 when the tub lid 86 is secured to the tub base82 as described in more detail below.

The flow plate 84 also comprises a frame or tub seal 94 that isconfigured to seal the perimeter of the tub base 82 when the tub lid 86is connected to the tub base 82. The frame seal 94 is connected to thedividing plate 96 by a plurality of supports, or bridges, 100. A gap 87is provided between the dividing plate 96 and the frame seal 94 by thebridges 100.

A water level indicator 102 is provided on the dividing plate 96 of theflow plate 84 to provide an indication of the water level. As shown inFIGS. 18-20, the water level indicator 102 may include a frusto-conicalportion. As shown in FIG. 23, the water level indicator 102 may be coneshaped. A small drain hole 104 is located in the bottom of the waterlevel indicator 102 to allow the water to fill up the water levelindicator 102 and then drain out of the bottom of the water levelindicator 102 to the tub base 82 as the water level decreases in the tubbase 82. The water level indicator 102 provides an indication of thewater level in the tub 20 by the water level indicator 102 being filledwith water once the water level in the tub base 82 reaches the level ofthe small drain hole 102, which then allows the water level in the tubbase 82 to be filled until the water in the water level indicator 102reaches the desired level such as that indicated by indicia 103.Although the water level indicator 102 provides an indication of thewater level, as the flow of breathable gas is directed to the surface ofthe water contained in the tub base 82, the water level is not criticalas the flow is in good contact with the surface of the water. The waterlevel indicator 102 may be provided with indicia 103 to indicate amaximum water level of the water tub 20. The light emitted from the PCBthrough the aperture 35 allows the water level in the water levelindicator 102 to be seen.

Referring to FIGS. 21-25, according to a sample embodiment of theinvention, the water tub 20 is configured to be disposable. The tub 20comprises the tub base 82 configured to contain a supply of water. Thetub lid 86 is provided on the tub base 82. The tub lid 86 may be securedto the tub base 82 by, for example, welding. The tub 20 may be formed,for example, of plastic material, metal or a combination of metal andplastic.

As shown in FIGS. 23 and 24, the flow plate 84 is provided on the tubbase 82. The tub lid 86 comprises the channel 90 that receives the flowof breathable gas generated by the flow generator 12 that enters thehumidifier 14 through the air inlet 22. As shown in FIG. 23, the channel90 comprises the channel outlet 92 that is received in the inlet 98 inthe dividing plate 96. The dividing plate 96 ensures that the flow ofbreathable gas flows across the whole tub as air enters into the centerand flows to the outside of the tub and then up through the gap 87between the walls of the tub base 82 and the dividing plate 96 to theoutlet 88 of the tub lid 86.

Referring to FIG. 25, the tub base 82 comprises a tub base rim 118 thatis engaged by a latch 130 of the tub lid 86 to connect the tub base 82and the tub lid 86. The frame seal 94 comprises a seal 112 that isprovided between the latch 130 of the tub lid 86 and the rim 118 at thetub base 82. A wedge 114 is provided on each bridge 100 and connected tothe seal 112 to force the seal 112 into a sealing engagement between therim 118 and a latch 130. The wedge 114 is engaged by a wedge 116 of thetub lid 86 to force the seal 112 into sealing engagement between the rim118 and the latch 130.

Humidifier Tub-Disposable-Second Embodiment

Referring to FIGS. 26-49, a humidifier tub that is configured to bedisposable according to another sample embodiment is illustrated. Thehumidifier tub 20 may comprise a tub base 82, a tub lid 86 having achannel 90. The tub lid 86 may also comprise a tub outlet 80 fordelivering a humidified flow of breathable gas. A tub emptying aperture89 may also be provided in the tub lid 86.

Referring to FIG. 27, the humidifier tub 20 may also comprise a flowplate 84 having a dividing plate 96. An inlet 98 is provided on thedividing plate 96 that corresponds to the outlet 92 (FIG. 28) of thechannel 90 of the tub lid 86. The dividing plate 96 of the flow plate 84is connected to a frame seal 94 by a plurality of bridges 100. A gap 87is provided between the frame seal 94 and the dividing plate 96.

Referring to FIGS. 27, 29, 30-32, 37-41, and 43-49, the humidifier tub20 may also include a water level indicator 102. The water levelindicator 102 may be provided on the dividing plate 96 of the flow plate84. As shown, for example, in FIG. 39, the water level indicator 102 mayhave a generally polygonal perimeter, including a generally rectangularportion 175 and a generally triangular portion 177. It should beappreciated, however, that other perimeter shapes may be provided forthe water level indicator 102, including regular polygonal shapes (e.g.square, rectangular, pentagonal), or polygonal shapes that arecombinations of regular polygonal shapes, or polygonal shapes combinedwith curvilinear surfaces.

As shown in FIGS. 31, 37, 39, 41, 43, 45, 46 and 49, the water levelindicator 102 comprises a drain hole 104 to allow the water to drain outof the bottom of the water level indicator 102 to the tub base 82. Asshown, for example, in FIG. 49, the drain hole 104 is not provided atthe bottom of the water level indicator 2, but is located at anintermediate position between the bottom and the top of the water levelindicator 102 to allow any pooled water to drain away from theintermediate position. In this embodiment the water level indicator 102is not filled with water but the water level is indicated against thesloping surface of the water level indicator as described in more detailbelow. As shown in FIG. 37, the drain hole 104 is located at a positiongenerally corresponding to the plane of the dividing plate 96 of theflow plate 84. As also shown in FIG. 37, and FIGS. 31, 38, 39, 41, 43,45 and 46, the water level indicator 102 may include indicia 103 thatindicates a maximum fill level of the humidifier tub 20. As shown in thefigures, the indicia 103 may be provided at the same level of the waterlevel indicator 102 as the drain hole 104.

Referring to FIG. 49, the generally triangular portion of the waterlevel indicator 102 extends below the frame seal 94 into the tub base 82when the tub is in the assembled condition and includes a first angledwall 109 and a second angled wall 111. As the water level of the tubbase 82 increases during fill up, the water level will initially contactthe bottom of the water level indicator 102. As the water levelcontinues to increase, the second angled wall 111 directs the waterlevel toward the drain hole 104 and the indicia 103 which are providedin the angled wall 111 between the frame seal 94 and the dividing plate96 of the flow plate. As the water level continues to increase andapproaches the drain hole 104, the visibility of the water levelrelative to the indicia 103 increases. As the indicia 103 is provided atthe same level as the drain hole 104, the maximum fill level of the tub20 is detected when the water level reaches the level of the drain hole104 and the indicia 103.

Referring to FIGS. 33, 35, 42 and 48, the seal 112 may be provided onthe periphery of the wedge 114 of the bridge 100. The wedge 116 of thetub lid 86 is configured to engage the wedge 114 of the dividing plate96 of the flow plate 84 to force the seal 112 between the rim 118 of thetub base 82 and the latch 130 of the tub lid 86. As shown in FIG. 48,the wedge 114 may comprise a flange 105 around its perimeter thatincludes a slot 107 that is configured to receive a portion of the seal112, as shown, for example, in FIG. 33.

Humidifier Tub-Disposable-Third Embodiment

Referring to FIGS. 50-62, a humidifier water tub 20 is configured to bedisposable according to still another sample embodiment as illustrated.The humidifier tub 20 comprises a tub base 82 and a tub lid 86. The tublid 86 includes an oval opening 300 and a sump region 340 that surroundsthe outlet 92 of the channel 90 that is formed in the tub lid 86 todirect the flow of air from the flow generator to the water contained inthe tub 20. The sump region 340 facilitates filling the tub 20 byproviding a larger area for entry of water than the outlet 92 of theflow channel 90.

The tub lid 86 also comprises a cover portion 301 that covers thesection of the flow channel 90 from the flow generator 12 to the inlet98 of the tub 20 that is angled down towards the flow generator 12. Thecover portion 301 prevents any water from flowing back into the flowgenerator 12 if the tub 20 was filled with water while still connectedto the flow generator 12 as water may only be poured into the tub in theregion provided by the opening 300 which is designed to channel thewater down towards the outlet 92.

As shown in FIGS. 53-62, a water level indicator 320 may be provided tothe humidifier tub 20 that is visible through the window 30 of the lid18. The water level indicator 320 may comprise a base portion 307 and anangled portion 303 extending from the base portion 307. The angledportion 303 may include markings 304 to indicate various water levels.The angled portion 303 may also include indicia 311 to indicate amaximum water fill level.

The water level indicator 320 may be removably connected to the dividingplate 96 of the flow plate 84 by posts 305. The posts 305 may beinserted into apertures 309 in the dividing plate 96 of the flow plate84. As shown in FIGS. 60a-60c , the posts 305 may include latches 313that are resiliently moveable with respect to the remaining portions ofthe posts 305. The latches 313 may be provided at the ends of legportions 315 which are attached to the base 307 of the water levelindicator 320. The leg portions 315 may be connected by a cross member317, as shown in FIGS. 59, 60 b and 61.

The water level indicator 320, for example, the angled portion 303, maybe formed of a colored plastic material, for example yellow. The waterlevel indicator 320 may be, for example, translucent. When the tub 20 isfilled with water, the water level indicator 320 may appear to changecolor, for example appearing slightly darker or a greenish-yellowishcolor as the water level rises.

As shown in the figures, the water level indicator 320 may be a roundedD-shape, although it should be appreciated that other shapes may beused. It should also be appreciated that the water level indicator 320may be attached to the dividing plate 96 of the flow plate 84 bystructures other than the post 305 as shown and described in thedrawings. For example, the water level indicator 320 may be adhered tothe dividing plate 96, or the water level indicator 320 may beintegrally formed, for example molded, with the dividing plate 96 of theflow plate 84.

Humidifier Tub-Reusable and Cleanable-First Embodiment

Referring to FIGS. 63-67, a tub 20 according to another embodiment ofthe invention is configured to be reusable, and cleanable. The tub base82 comprises a plurality of clips 106 that are configured to engage andretain the tub lid 86 in connection with the tub base 82. A clip 108 isalso provided and comprises an aperture 110 to accommodate the outlet 88of the flow plate, as shown in FIG. 63.

The flow plate 84 is configured to be removable from the tub base 82 andit is not permanently secured to the tub base 82. As shown in FIGS. 65and 67, the bridges 100 of the flow plate 84 include a wedge 114 that isconnected to a seal 112. The seal 112 is forced into sealing engagementbetween a rim 120 of the tub lid 86 and the rim 118 of the tub base 82.The clip 106 is provided to clip the tub lid 86 to the tub base 82 withthe seal 112 secured in between in sealing engagement. A first portion124 of the clip 106 engages the tub base 82 up to the rim 118 and asecond portion 126 of the clip 106 is configured to engage a projection128 of the tub lid 86 to secure the tub lid 86 and the tub base 82 inengagement.

The humidifier 14 does not include any seals that are provided under thewater supply of the tub base 82. The lid 18 comprises the seal 19 toallow for pressurizing of the humidifier chamber 16 with the flowprovided by the flow generator 12 to reduce the pressure on the tubjoints, including the disposable tub and the reusable, cleanable tub,thus reducing leaks. Pressurizing the humidifier chamber also reducestolerances for insertion of the water tub with respect to seals on theinlet of the humidifier and the outlet tube 70 of the humidifier 14. Thesealing ring 76 provided to the outlet tube 70 is provided on an outersurface of the humidifier cradle 32 and not provided under the water ofthe supply contained in the tub base 82.

Humidifier Tub-Reusable and Cleanable-Second Embodiment

Referring to FIGS. 68-72, a water tub 20 according to another sampleembodiment is configured to be reusable and cleanable. The tub 20 mayhave a water level indicator 320 similar to the water level indicatordescribed with respect to the previous embodiments. It should beappreciated that the tub 20 may be provided with any of the water levelindicators described herein.

The tub lid 86 may include the cover portion 301 to cover the inletregion of the flow channel 90 adjacent to the inlet 22 of the humidifier14 that is connected to the flow generator 12.

As shown in FIGS. 68-72, the tub lid 86 may be secured to the tub base82 by a plurality of clips 106, 108. The clip 108 may have an apertureconfigured to accommodate the outlet 88 of the tub 20. The tub lid 86may include projections 128 that are received in apertures 129 in theclips 106. The tub lid 86 may also include projections 152 that arereceived in apertures 151 provided in the clip 108.

As also shown in FIGS. 68-72, the tub lid 86 may include recesses 330 toaccommodate the fingers of a user of the tub 20 to provide a spacebetween the tub lid 86 and the clips 106 as the user inserts the tub lid86 on to the tub base 82 so that the projections 128 are received in theapertures 129. The recesses 330 may also accommodate the fingers duringremoval of the lid 86 from the base 82, for example to allow the partsof the tub 20 to be disassembled and cleaned.

It should be appreciated that the reusable and cleanable tubs mayinclude a water level indicator as discussed above with respect to theembodiments of the disposable tub. It should also be appreciated thatthe reusable and cleanable tubs may include more than one water levelindicator as discussed above with respect to the embodiments discussedabove. It should further be appreciated that the water level indicator,or indicators, or the tub may not include indicia to include a maximumwater level.

Heated Tube

Referring to FIG. 73, a heated tube 134 is connectable to the outlettube 70 of the humidifier 14. The heated tube 134 comprises a cuff 136that includes a humidifier connector 138 that is configured to beconnected to the tube connector 50 of the humidifier 14. The humidifierconnector 138 comprises terminals 140 that are configured to receive thecontacts 78 of the tube connector 50 when the humidifier connector 138and the tube connector 50 are connected. The cuff 136 may be formed asdescribed, for example, in U.S. application Ser. No. 11/936,822, theentire contents of which are incorporated herein by reference. Theheated tube may include, for example, two or three wires and maytransmit and receive signals to and from a controller in the humidifierand/or the flow generator as described in U.S. application Ser. No.11/936,822. The end of the humidifier connector 138 that is configuredfor insertion into the tube connector 50 of FIG. 15 may include an angle200 to facilitate insertion of the connector 138 into the tube connector50. The angle 200 may be between about 15°-35°.

Referring to FIGS. 74-76, the heated tube 134 may be connected to apatient interface, e.g. a mask, by a cuff 142 provided at the end of theheated tube 134. An aerofoil fixture 144 is provided in the cuff 142 andincludes a thermistor 148, as shown in FIG. 75. The shape of theaerofoil fixture 144 provides a smooth flow around the aerofoil fixture144 so that the thermistor 148 provides a good reading of thetemperature of the flow of breathable gas in the tube 134. The cuff 142may be formed by, for example, overmolding on a pre-block 146, or anymethod disclosed, for example, in U.S. application Ser. No. 11/936,822.The thermistor 148 is connected to the wires in the heated tube 134 bylead frames 150. The temperature sensed by the thermistor 148 may beprovided as a signal from the thermistor 148 through the lead frames 150and the wires to a controller located in the humidifier and/or the flowgenerator.

The tube 134 may have a 15 mm internal diameter. The tube 134 may beheated using wires as described in U.S. application Ser. No. 11/936,822.A non-heated 15 mm air delivery tube my also be used. The 15 mm internaldiameter tube may be connected to the tube connector 50 and the patientinterface using a 22 mm isotaper connection.

While the invention has been described in connection with what arepresently considered to be the most practical and preferred embodiments,it is to be understood that the invention is not to be limited to thedisclosed embodiments, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the invention. Also, the various embodiments described abovemay be implemented in conjunction with other embodiments, e.g., aspectsof one embodiment may be combined with aspects of another embodiment torealize yet other embodiments. Further, each independent feature orcomponent of any given assembly may constitute an additional embodiment.Furthermore, each individual component of any given assembly, one ormore portions of an individual component of any given assembly, andvarious combinations of components from one or more embodiments mayinclude one or more ornamental design features. In addition, while theinvention has particular application to patients who suffer from OSA, itis to be appreciated that patients who suffer from other illnesses(e.g., congestive heart failure, diabetes, morbid obesity, stroke,barriatric surgery, etc.) can derive benefit from the above teachings.Moreover, the above teachings have applicability with patients andnon-patients alike in non-medical applications.

In this specification, the word “comprising” is to be understood in its“open” sense, that is, in the sense of “including”, and thus not limitedto its “closed” sense, that is the sense of “consisting only of”. Acorresponding meaning is to be attributed to the corresponding words“comprise,” “comprised” and “comprises” where they appear.

It will further be understood that any reference herein to known priorart does not, unless the contrary indication appears, constitute anadmission that such prior art is commonly known by those skilled in theart to which the invention relates.

What is claimed is:
 1. A respiratory apparatus for providing ahumidified flow of pressurised breathable gas to a patient, comprising:a flow generator to generate a flow of pressurised breathable gas to bedelivered to a patient; a pressurisable humidifier chamber including achamber inlet configured to receive the flow of pressurised breathablegas from the flow generator, the chamber having a rear wall comprising achamber outlet, the chamber having a bottom support surface including aheating plate having a substantially upward-facing heating surface; ahumidifier lid being hingedly attached to a wall of the chamber andpivotably movable between an open position and a closed position, aninside surface of the humidifier lid having a depending rib; a water tubconfigured to contain a supply of water, the tub having a tub base witha bottom adapted to contact the heating surface, a tub lid, and a tubseal sealing between the tub base and the tub lid and located above thesupply of water, the tub lid having a tub inlet and a tub outlet, thetub outlet being provided on a rear wall of the tub and configured todeliver the flow of pressurised breathable gas with added humidity tothe chamber outlet, the tub being constructed and dimensioned to bewholly positionable within the chamber; a chamber seal configured toseal the chamber such that the flow of pressurised breathable gaspressurises the chamber when the tub is wholly within the chamber andthe humidifier lid is in the closed position, the chamber seal having agroove configured to receive the depending rib of the humidifier lid,the chamber seal having a sealing rim that extends around a perimeter ofthe chamber seal, the sealing rim having a perimeter that is larger thana perimeter of the tub lid so as to be positioned above and sealdownwardly against a substantially upward-facing surface of the chamberwhen the humidifier lid is in the closed position; and a clip to forcethe tub seal into sealing engagement and to secure the tub lid and thetub base to one another.
 2. The respiratory apparatus according to claim1, further comprising an outlet seal to seal between the chamber outletand the tub outlet.
 3. The respiratory apparatus according to claim 2,wherein the outlet seal includes a lip that projects into the chamber,the lip being mounted on a flange that is seated in a recess provided inan inner surface of the rear wall.
 4. The respiratory apparatusaccording to claim 1, further comprising mutually engaging surfaces ofthe chamber and the tub configured to urge the tub in a rearwardhorizontal direction towards the chamber outlet to facilitate sealingbetween the tub outlet and the chamber outlet.
 5. The respiratoryapparatus according to claim 1, wherein the sealing rim has a profile asseen in cross section that curves downward and inwardly towards thechamber, such that the sealing rim is structured to be exposed to theflow of pressurised breathable gas provided to the chamber.
 6. Therespiratory apparatus according to claim 1, wherein the tub inlet isspaced away from the chamber inlet by a distance when the tub isreceived in the chamber.
 7. The respiratory apparatus according to claim1, wherein the depending rib is spaced inwardly from an outermost borderof the humidifier lid, at least a portion of the chamber seal beingpositioned substantially between the depending rib and the outermostborder when the humidifier lid is in the closed position.
 8. Therespiratory apparatus according to claim 1, further comprising laterallyspaced recesses formed in the tub lid to accommodate the fingers of auser for handling the tub.
 9. The respiratory apparatus according toclaim 1, wherein the chamber seal is selectively engageable with the tublid.
 10. The respiratory apparatus according to claim 1, wherein, whenthe humidifier lid is in the closed position with the tub in thechamber, the humidifier lid pushes the tub against the heating plate.11. The respiratory apparatus according to claim 1, wherein the chamberseal comprises at least one first protrusion configured to engage thetub, wherein the at least one first protrusion is wedge-shaped.
 12. Therespiratory apparatus according to claim 11, wherein the chamber sealcomprises at least one second protrusion configured to push against thetub lid when the humidifier lid is in the closed position.
 13. Therespiratory apparatus according to claim 1, wherein the tub has asubstantially polygonal shape having four corners, three of whichcorners are similarly rounded corners and the fourth corner has adifferent shape compared to the three similarly rounded corners.
 14. Therespiratory apparatus according to claim 1, further comprising auser-operated lid closure member to maintain the humidifier lid in theclosed position, the user-operated lid closure member comprising: atleast one latch to selectively engage with a catch; a spring to bias thelatch into engagement with the catch; a post to support the spring; andan opening member configured to be pushed against the bias of the springto release the latch from the catch, thus allowing the humidifier lid tobe pivoted to the open position.
 15. The respiratory apparatus accordingto claim 1, further comprising a water level indicator to indicate amaximum fill level for the water tub, the water level indicator beingsuspended within the tub for direct exposure to water within the tub,the water level indicator having an angled wall having a first portionextending into the tub to a first depth and a second portion extendinginto the tub to a second depth that is different than the first depth,wherein as the water level of the tub base increases when filling thetub, the water level will initially contact the first portion of theangled wall of the water level indicator, and as the water levelcontinues to increase, the water will then rise upwardly towards thesecond portion of the angled wall to contact indicia indicating themaximum fill level, the indicia on the angled wall being positioned soas to be visible when the water tub is viewed from above.
 16. Therespiratory apparatus according to claim 1, wherein the rear wallcomprises an outlet tube, and the respiratory apparatus furthercomprises a gas delivery tube with a first end connectable to the outlettube to receive the flow of breathable gas, and a second end including acuff configured for connection to a patient interface.
 17. Therespiratory apparatus according to claim 1, wherein the tub lid has awater aperture, and the chamber seal further comprises an aperture sealprojecting from an underside of the chamber seal to seal the wateraperture.
 18. The respiratory apparatus according to claim 1, whereinthe tub is removable from the humidifier chamber and is configured toprevent water from flowing back into the flow generator.
 19. Therespiratory apparatus according to claim 1, wherein the clip is locatedalong a lateral side of the tub.
 20. The respiratory apparatus accordingto claim 19, wherein the clip is mounted for pivotable movement betweenan open position and a closed position, the clip being pivotable aboutan axis located at a proximal end of the clip, the clip having a slotconfigured to receive a projection of the tub when the clip is pivotedfrom the open position to the closed position, the slot and theprojection extending parallel to the axis, and the slot being positionedcloser to the proximal end of the clip as compared to a distal end ofthe clip.
 21. The respiratory apparatus according to claim 1, wherein:the respiratory apparatus further comprises an outlet seal to sealbetween the chamber outlet and the tub outlet, the outlet seal includesa lip that projects into the chamber, the lip being mounted on a flangethat is seated in a recess provided in an inner surface of the rearwall, the sealing rim has a profile as seen in cross section that curvesdownward and inwardly towards the chamber, such that the sealing rim isstructured to be exposed to the flow of pressurised breathable gasprovided to the humidifier chamber, the tub inlet is spaced away fromthe chamber inlet by a distance when the tub is received in the chamber,the depending rib is spaced inwardly from an outermost border of thehumidifier lid, at least a portion of the chamber seal being positionedsubstantially between the depending rib and the outermost border whenthe humidifier lid is in the closed position, the respiratory apparatusfurther comprises laterally spaced recesses formed in the tub lid toaccommodate the fingers of a user for handling the tub, the chamber sealis selectively engageable with the tub lid, when the humidifier lid isin the closed position with the tub in the chamber, the humidifier lidpushes the tub against the heating plate, wherein: the chamber sealcomprises at least one first protrusion configured to engage the tub,wherein the at least one first protrusion is wedge-shaped, the chamberseal comprises at least one second protrusion configured to push againstthe tub lid when the humidifier lid is in the closed position, the tubhas a substantially polygonal shape having four corners, three of whichcorners are similarly rounded corners and the fourth corner has adifferent shape compared to the three similarly rounded corners, furthercomprising a user-operated lid closure member to maintain the humidifierlid in the closed position, the user-operated lid closure membercomprising: at least one latch to selectively engage with a catch; aspring to bias the latch into engagement with the catch; and a post tosupport the spring; wherein the catch and the latch are configured to bereleased from one another by pushing against the bias of the spring,thus allowing the humidifier lid to be pivoted to the open position, therespiratory apparatus further comprises a water level indicator toindicate a maximum fill level for the water tub, the water levelindicator being suspended within the tub for direct exposure to waterwithin the tub, the water level indicator having an angled wall having afirst portion extending into the tub to a first depth and a secondportion extending into the tub to a second depth that is different thanthe first depth, wherein as the water level of the tub base increaseswhen filling the tub, the water level will initially contact the firstportion of the angled wall of the water level indicator, and as thewater level continues to increase, the water will then rise upwardlytowards the second portion of the angled wall to contact indiciaindicating the maximum fill level, the indicia on the angled wall beingpositioned so as to be visible when the water tub is viewed from above,the rear wall comprises an outlet tube, and the respiratory apparatusfurther comprises a gas delivery tube with a first end connectable tothe outlet tube to receive the flow of breathable gas, and a second endincluding a cuff configured for connection to a patient interface, thetub lid has a water aperture, and the chamber seal further comprises anaperture seal projecting from an underside of the chamber seal to sealthe water aperture, the tub is removable from the humidifier chamber andis configured to prevent water flowing out of the tub from flowing backinto the flow generator, the clip is located along a lateral side of thetub, and the clip is mounted for pivotable movement between an openposition and a closed position, the clip being pivotable about an axislocated at a proximal end of the clip, the clip having a slot configuredto receive a projection of the tub when the clip is pivoted from theopen position to the closed position, the slot and the projectionextending parallel to the axis, and the slot being positioned closer tothe proximal end of the clip as compared to a distal end of the clip.22. The respiratory apparatus according to claim 1, wherein: therespiratory apparatus further comprises an outlet seal to seal betweenthe chamber outlet and the tub outlet, the outlet seal includes a lipthat projects into the chamber, the lip being mounted on a flange thatis seated in a recess provided in an inner surface of the rear wall, thedepending rib is spaced inwardly from an outermost border of thehumidifier lid, at least a portion of the chamber seal being positionedsubstantially between the depending rib and the outermost border whenthe humidifier lid is in the closed position, the respiratory apparatusfurther comprises laterally spaced recesses formed in the tub lid toaccommodate the fingers of a user for handling the tub, when thehumidifier lid is in the closed position with the tub in the chamber,the humidifier lid pushes the tub against the heating plate, wherein:the chamber seal comprises at least one first protrusion configured toengage the tub, wherein the at least one first protrusion iswedge-shaped, and the chamber seal comprises at least one secondprotrusion configured to push against the tub lid when the humidifierlid is in the closed position, the tub has a substantially polygonalshape having four corners, three of which corners are similarly roundedcorners and the fourth corner has a different shape compared to thethree similarly rounded corners, the respiratory apparatus furthercomprises a latch and catch to maintain the humidifier lid in the closedposition, the respiratory apparatus further comprises a water levelindicator to indicate a maximum fill level for the water tub, the waterlevel indicator being suspended within the tub for direct exposure towater within the tub, the water level indicator having an angled wallhaving a first portion extending into the tub to a first depth and asecond portion extending into the tub to a second depth that isdifferent than the first depth, wherein as the water level of the tubbase increases when filling the tub, the water level will initiallycontact the first portion of the angled wall of the water levelindicator, and as the water level continues to increase, the water willthen rise upwardly towards the second portion of the angled wall tocontact indicia indicating the maximum fill level, the indicia on theangled wall being positioned so as to be visible when the water tub isviewed from above, the rear wall comprises an outlet tube, and therespiratory apparatus further comprises a gas delivery tube with a firstend connectable to the outlet tube to receive the flow of breathablegas, and a second end including a cuff configured for connection to apatient interface, and the clip is mounted for pivotable movementbetween an open position and a closed position, the clip being pivotableabout an axis located at a proximal end of the clip, the clip having aslot configured to receive a projection of the tub when the clip ispivoted from the open position to the closed position, the slot and theprojection extending parallel to the axis, and the slot being positionedcloser to the proximal end of the clip as compared to a distal end ofthe clip.
 23. The respiratory apparatus according to claim 1, wherein:the respiratory apparatus further comprises an outlet seal to sealbetween the chamber outlet and the tub outlet, the outlet seal includesa lip that projects into the chamber, the lip being mounted on a flangethat is seated in a recess provided in an inner surface of the rearwall, the depending rib is spaced inwardly from an outermost border ofthe humidifier lid, at least a portion of the chamber seal beingpositioned substantially between the depending rib and the outermostborder when the humidifier lid is in the closed position, therespiratory apparatus further comprises laterally spaced recesses formedin the tub lid to accommodate the fingers of a user for handling thetub, when the humidifier lid is in the closed position with the tub inthe chamber, the humidifier lid pushes the tub against the heatingplate, the respiratory apparatus further comprises a user-operated lidclosure member to maintain the humidifier lid in the closed position,the user-operated lid closure member comprising at least one latch toselectively engage with a catch; a spring to bias the latch intoengagement with the catch; and an opening member configured to be pushedagainst the bias of the spring to release the latch from the catch, thusallowing the humidifier lid to be pivoted to the open position, therespiratory apparatus further comprises a water level indicator toindicate a maximum fill level for the water tub, the water levelindicator being suspended within the tub for direct exposure to waterwithin the tub, the water level indicator having an angled wall having afirst portion extending into the tub to a first depth and a secondportion extending into the tub to a second depth that is different thanthe first depth, wherein as the water level of the tub base increaseswhen filling the tub, the water level will initially contact the firstportion of the angled wall of the water level indicator, and as thewater level continues to increase, the water will then rise upwardlytowards the second portion of the angled wall to contact indiciaindicating the maximum fill level, the indicia on the angled wall beingpositioned so as to be visible when the water tub is viewed from above,the tub lid has a water aperture, and the chamber seal further comprisesan aperture seal projecting from an underside of the chamber seal toseal the water aperture, and the clip is mounted for pivotable movementbetween an open position and a closed position, the clip being pivotableabout an axis located at a proximal end of the clip, the clip having aslot configured to receive a projection of the tub when the clip ispivoted from the open position to the closed position, the slot and theprojection extending parallel to the axis.
 24. A respiratory apparatusfor providing a humidified flow of pressurised breathable gas to apatient, comprising: a flow generator to generate a flow of pressurisedbreathable gas to be delivered to a patient; a pressurisable humidifierchamber including a chamber inlet configured to receive the flow ofpressurised breathable gas from the flow generator, the chamber having arear wall comprising a chamber outlet, the chamber having a bottomsupport surface including a heating plate having a substantiallyupward-facing heating surface; a humidifier lid being hingedly attachedto a wall of the chamber and pivotably movable between an open positionand a closed position; a water tub configured to contain a supply ofwater, the tub having a tub base with a bottom adapted to contact theheating surface, a tub lid, and a tub seal sealing between the tub baseand the tub lid and located above the supply of water, the tub lidhaving a tub inlet and a tub outlet, the tub outlet being provided on arear wall of the tub and configured to deliver the flow of pressurisedbreathable gas with added humidity to the chamber outlet, the tub beingconstructed and dimensioned to be wholly positionable within thechamber; and a seal including a central portion and an outer perimeterportion surrounding the central portion, wherein the outer perimeterportion has a chamber seal configured to seal the chamber such that theflow of breathable gas pressurises the chamber, wherein the centralportion has 1) at least one first protrusion configured to engage thetub lid, wherein the at least one first protrusion is wedge-shaped, 2)at least one second protrusion configured to push against the tub lidwhen the humidifier lid is in the closed position, and 3) an apertureseal projecting from an underside of the seal to seal a water apertureof the tub lid.
 25. The respiratory apparatus according to claim 24,further comprising a water level indicator to indicate a fill level forthe water tub, the water level indicator being suspended within the tubfor direct exposure to water within the tub, the water level indicatorhaving an angled surface, wherein as the water level of the tub baseincreases when filling the tub, the water level will initially contact abottom of the angled surface of the water level indicator, and as thewater level continues to increase, the water will then contact indiciatowards a top of the angled surface indicating the fill level.
 26. Therespiratory apparatus according to claim 24, further comprising a clipto secure the tub lid and the tub base to one another, the clip beinglocated along a lateral side of the tub, the clip being mounted on thetub for pivotable movement about an axis located at a proximal end ofthe clip, the clip having a slot configured to receive a projection ofthe tub when the clip is pivoted to a secured position, the slotextending parallel to the axis and being positioned closer to theproximal end of the clip as compared to a distal end of the clip. 27.The respiratory apparatus according to claim 24, wherein: the seal has agroove configured to receive an edge of the humidifier lid, the chamberseal includes a sealing rim that extends about a perimeter of the seal,the sealing rim having a profile as seen in cross section that projectsdownwards from the humidifier lid and curves inwardly towards thechamber, the sealing rim extending beyond the edge of the tub lid alongthe entire perimeter of the tub lid, the sealing rim being adapted toengage an upwardly facing rim surrounding the chamber, the tub lidincludes a water opening and the seal includes a sealing ring to sealthe water opening, the sealing ring projecting downwards from anunderside of the seal, and the tub lid has laterally spaced recesses toaccommodate the fingers of a user for handling the tub.
 28. Arespiratory apparatus for providing a humidified flow of pressurizedbreathable gas to a patient, comprising: a flow generator to generate aflow of pressurized breathable gas to be delivered to a patient; achamber configured to receive the flow of pressurized breathable gas,the chamber having a chamber inlet to deliver the pressurized breathablegas from the flow generator to the chamber, the chamber having a chamberoutlet to deliver the flow of breathable gas to an outlet tube, thechamber having a bottom support surface having a heating plate; a tubeconnector in fluid communication with the chamber outlet; a tubconfigured to contain a supply of water, the tub being configured to beinserted into the chamber, the tub having a tub base, a tub lid and atub seal between the tub lid and the tub base, the tub base having witha bottom adapted to contact the heating plate, the tub lid having a tubinlet and a tub outlet, the tub outlet being configured to deliver thehumidified flow of breathable gas to the chamber outlet; a latchengagable with a catch to maintain the tub within the chamber; auser-operated opening member configured to be pushed to release thelatch from the catch, thus allowing the tub to be removed from thechamber; a clipping structure to force the tub seal into sealingengagement and to secure the tub lid and the tub base to one another,the clipping structure being located along a lateral side of the tub,the clipping structure including a clip mounted for movement towards andaway from the lateral side of the tub, the clip having a pair oflaterally spaced slots each configured to receive a projection of thetub when the clip is moved to a closed position, wherein the clippingstructure is configured to force a rim of the tub lid into sealingengagement with a rim of the tub base; and a water level indicator toindicate a maximum fill level for the water tub.
 29. The respiratoryapparatus according to claim 28, further comprising an outer rim, acircular inlet, and a plurality of bridges that connect the outer rim tothe circular inlet, the tub seal being supported by the outer rim, thecircular inlet being aligned with the tub inlet such that the flow ofpressurized breathable gas is directed from the tub inlet to thecircular inlet when the tub base, the tub lid and the tub seal areconnected.
 30. A respiratory apparatus for providing a humidified flowof pressurized breathable gas to a patient, comprising: a flow generatorto generate a flow of pressurized breathable gas to be delivered to apatient; a pressurizable humidifier chamber including a chamber inletconfigured to receive the flow of pressurized breathable gas from theflow generator, the chamber having a rear wall including an innersurface including a chamber outlet, the rear wall including an outlettube protruding from an outer surface of the rear wall, the chamberhaving a bottom support surface including a heating plate; a humidifierlid pivotable between an open position and a closed position, thehumidifier lid having an outside surface and an inside surface, theinside surface having a depending rib, the humidifier lid comprising ahinge portion that is hingedly attached to a hinge portion provided onthe rear wall of the chamber; a water tub configured to contain water,the tub having a tub base with a bottom adapted to contact the heatingplate, a tub lid, and a tub seal sealing between the tub base and thetub lid, the tub lid having a tub inlet and a tub outlet, the tub outletbeing provided on a rear wall of the tub and configured to deliver theflow of pressurized breathable gas with added humidity to the chamberoutlet, the tub lid having a water aperture; a chamber seal between thehumidifier lid and the tub lid when the tub is in the chamber and thehumidifier lid is in the closed position, the chamber seal beingconfigured to seal the chamber such that the flow of breathable gaspressurizes the chamber with the tub as a whole positioned therein, thechamber seal having a groove configured to receive the depending rib ofthe humidifier lid, the chamber seal having a sealing rim that extendsaround the perimeter of the chamber seal, the sealing rim positionedabove and sealing downwardly against a substantially horizontal surfaceof the chamber when the humidifier lid is in the closed position, thechamber seal further comprising a circular sealing ring projecting froman underside of the chamber to seal the water aperture; and a clippingstructure to force the tub seal into sealing engagement and to securethe tub lid and the tub base to one another, the clipping structurebeing located along a lateral side of the tub, the clipping structureincluding a clip mounted for pivotable movement between an open positionin which the tub lid may be lifted relative to the tub base and a closedposition in which the tub lid is secured against relative movementrelative to the tub base, the clip being pivotable about an axis locatedat a proximal end of the clip, the clip having a slot configured toreceive a projection of the tub when the clip is pivoted from the openposition to the closed position, the slot and the projection extendingparallel to the axis, and the slot being positioned closer to theproximal end of the clip as compared to a distal end of the clip.